Method of preparing a polymer, method of preparing a compounds, compounds, polymers, and method of manufacturing an electronic device

ABSTRACT

A polymer comprising structural units of the formula I is prepared according to a novel method, in which the starting compound R 1  ‘S—(CHR’ 2 )—Ar—(CHR 2 )—SR 1  is polymerized with a base, preferably in an aprotic solvent. The polymer comprises 50 to 1000 structural units of the formula I. The solution comprising the polymer thus prepared has a lower viscosity than a solution of a similar polymer with a greater chain length. The solution comprising the polymer thus prepared may be applied as a layer on a substrate. Electronic components with layers prepared with the polymer of the invention show better properties.

Method of preparing a polymer, method of preparing a compound,compounds, polymers, and method of manufacturing an electronic device

The invention relates to a method of preparing a polymer which comprisesstructural units of formula I,

in which formula:

-   Ar is an aromatic cyclic system with 4 to 20 carbon atoms, which may    be substituted with a substituent chosen from among a non-branched    C₁-C₂₀-alkyl, C₃-C₂₀-alkoxy, C₁-C₂₀-alkylsulfate, a branched    C₃-C₂₀-alkyl, phenyl or benzyl group and which may comprise up to 4    heteroatoms chosen from the group comprising oxygen, sulfur, and    nitrogen in the aromatic cyclic system,-   t is equal to 0, 1, or 2,-   R₁ is chosen from the group comprising a non-branched C₁-C₂₀-alkyl    group, a branched C₃-C₂₀ alkyl group, a cyclic C₄-C₂₀-alkyl group, a    C₁-C₄-alkyl-substituted cyclic C₄-C₂₀-alkyl group, a phenyl group    and a benzyl group, which groups may comprise heteroatoms,-   R₂ and R″₂ are chosen from the group comprising a hydrogen atom and    a C₁-C₂₀-alkyl and C₄-C₂₀-aryl group, which groups may comprise    substituents.

The invention also relates to a method of preparing compounds having theformula II

in which formula:

-   Ar is an aromatic cyclic system with 4 to 20 carbon atoms, which may    be substituted with a substituent chosen from among a non-branched    C₁-C₂₀-alkyl, C₃-C₂₀-alkoxy, C₁-C₂₀-alkylsulfate, a branched    C₃-C₂₀-alkyl, phenyl or benzyl group and which may comprise up to 4    heteroatoms chosen from the group comprising oxygen, sulfur, and    nitrogen in the aromatic cyclic system,-   R₁ and R₁′ are chosen from the group comprising a non-branched    C₁-C₂₀-alkyl group, a branched C₃-C₂₀ alkyl group, a cyclic alkyl    group, a C₁-C₄-alkyl-substituted cyclic alkyl group, a C₄-C₁₄-aryl    group, and a benzyl group, which groups may comprise heteroatoms,-   R₂ and R₂′ are chosen from the group comprising a hydrogen atom and    a C₁-C₂₀-alkyl and a C₄-C₂₀-aryl group, which groups may comprise    substituents.

The invention also relates to compounds and polymers.

The invention further relates to a composition of polymers.

The invention further relates to a method of preparing a polymer withstructural units having the formula VI,

in which Formula:

-   Ar is an aromatic cyclic system with 4 to 20 carbon atoms, which may    be substituted with a substituent chosen from among a non-branched    C₁-C₂₀-alkyl, C₃-C₂₀-alkoxy, C₁-C₂₀-alkylsulfate, a branched    C₃-C₂₀-alkyl, phenyl or benzyl group and which may comprise up to 4    heteroatoms chosen from the group comprising oxygen, sulfur, and    nitrogen in the aromatic cyclic system, and-   R₂ and R″₂ are chosen from the group comprising a hydrogen atom and    a C₁-C₂₀-alkyl and C₄-C₂₀-aryl group, which groups may comprise    substituents.

The invention further relates to a method of manufacturing a layer of apolymer with structural units having the formula VI,

in which formula:

-   Ar is an aromatic cyclic system with 4 to 20 carbon atoms, which may    be substituted with a substituent chosen from among a non-branched    C₁-C₂₀ -alkyl, C₃-C₂₀-alkoxy, C₁-C₂₀-alkylsulfate, a branched    C₃-C₂₀-alkyl, phenyl or benzyl group and which may comprise up to 4    heteroatoms chosen from the group comprising oxygen, sulfur, and    nitrogen in the aromatic cyclic system, and-   R₂ and R″₂ are chosen from the group comprising a hydrogen atom and    a C₁-C₂₀-alkyl and C₄-C₂₀-aryl group, which groups may comprise    substituents,    which method comprises    -   the application of a solution of the polymer comprising        structural units having the formula I as a layer on a substrate,

-   -   in which formula I:    -   t is equal to 0, 1 or 2,    -   R₁ is chosen from the group comprising a non-branched        C₁-C₂₀-alkyl group, a branched C₃-C₂₀ alkyl group, a cyclic        C₄-C₂₀-alkyl group, a C₁-C₄-alkyl-substituted cyclic        C₄-C₂₀-alkyl group, a phenyl group, and a benzy group, which        groups may comprise heteroatoms, and    -   R₂, R″₂, and Ar are equal to R₂, R″₂ and Ar in formula VI, and    -   the conversion through heating of the polymer comprising        structural units of the formula I into the polymer comprising        structural units of the formula VI.

The invention further relates to an electronic device comprising a layerof a polymer with mainly the structural units having the formula VI:

in which formula:

-   Ar is an aromatic cyclic system with 4 to 20 carbon atoms, which may    be substituted with a substituent chosen from among a non-branched    C₁-C₂₀-alkyl, C₃-C₂₀-alkoxy, C₁-C₂₀-alkylsulfate, a branched    C₃-C₂₀-alkyl, phenyl or benzyl group and which may comprise up to 4    heteroatoms chosen from the group comprising oxygen, sulfur, and    nitrogen in the aromatic cyclic system, and-   R₂ and R″₂ are chosen from the group comprising a hydrogen atom and    a C₁-C₂₀-alkyl and C₄-C₂₀-aryl group, which groups may comprise    substituents.

Such a method of preparing a polymer is known from EP-B 705857. In theknown method, the polymer is prepared from a compound having the formulaX:

in which formula Y and Y′ each represent a leaving group such as Cl, Br,F, tosylatc.

A reaction of the compound with formula X with a thiole R₁SH yields anon-symmetrical intermediate product, a compound in accordance with theformula X in which Y′ is equal to SR₁. Purification then takes place bymeans of column chromatography, followed by oxidation and polymerizationof this intermediate product into the polymer with structural unitshaving the formula I. This polymer may be provided as a layer on asubstrate, whereupon the group S(O)_(t)R₁ is eliminated.

A disadvantage of the known method of preparing a polymer is that thepurification step by means of column chromatography is time-consumingand difficult to industrialize. A disadvantage of the known method ofpreparing a compound of the formula II is that usually the toxic HCl gasis used for preparing the basic ingredient. A disadvantage of the knownmethod of preparing a compound with structural units according to theformula VI, e.g. the elimination of the S(O)_(t)R₁-group from thepolymer having structural units of the formula I, is thatS(O)_(t)R₁-groups with t unequal to 1 are eliminated at highertemperatures or not at all. A disadvantage of the known method ofmanufacturing a layer is that the solution of the polymer havingstructural units of the formula I has a high viscosity, i.e. ofapproximately 100×10⁻³ Pa·s. Filtering of the solution and the processof providing the layer on the substrate are sluggish processes owing tothe high viscosity.

It is a first object of the invention to provide a method of preparing apolymer of the kind mentioned in the opening paragraph which can bereadily implemented on an industrial scale.

It is a second object of the invention to provide a method of preparinga compound of the kind mentioned in the opening paragraphs wherein notoxic gases are used for the conversion of H—Ar—H into the basicingredient.

It is a third object of the invention to provide a method of preparing apolymer having structural units of the formula I, as mentioned in theopening paragraphs, which results in a polymer with a chain conjugationthat is substantially larger.

It is a fourth object of the invention to provide a method ofmanufacturing a layer of the kind mentioned in the opening paragraphswhich is not hampered by the viscosity.

It is a fifth object of the invention to provide an electronic device ofthe kind mentioned in the opening paragraphs which has improvedproperties.

The first object is realized in that the method starts with a compoundhaving the formula II

in which formula

-   R′₁ is chosen from the group comprising a non-branched C₁-C₂₀-alkyl    group, a branched C₃-C₂₀ alkyl group, a cyclic alkyl group, a    C₁-C₄-alkyl-substituted cyclic alkyl group, a phenyl and a benzyl    group, which groups may comprise heteroatoms,-   R₁, R₂, and Ar are equal to R₁, R₂, and Ar in formula I, and-   R′₂ is chosen from the group comprising a hydrogen atom and a    C₁-C₂₀-alkyl and C₄-C₂₀-aryl group, which groups may comprise    substituents,-   and that the polymer with structural units of the formula I is    converted through polymerization with the aid of a base into a    polymer which comprises units having the formula III

in which formula

-   -   R₁, R₂, and Ar are equal to R₁, R₂, and Ar in formula II, and    -   R′₂ is chosen from the group comprising R₂ and R′₂, and through        oxidation of at least a number of the units of the polymer        having the formula III for the preparation of the polymer with        units having the formula I, in which formula t is equal to 1 or        2.

The monomer in the method according to the invention—the compound havingthe formula II—has a thioalkyl group R₁S, R′₁S on either side prior tothe polymerization step. This is advantageous because no purificationstep is now necessary for obtaining the compound having the formula IIin a substantially pure form. The monomer is created by means of atleast two molar equivalents of thiole to one molar equivalent of thebasic substance—the compound having the formula X—instead of anon-symmetrical compound which has a thioalkyl group at one side of theAr group only. An additional advantage is that the monomer may inprinciple also be prepared from other basic substances than the compoundhaving the formula X, which can be prepared with hazardous chemicalsonly, such as a compound H—Ar—H.

It is surprising that the polymerization step can be carried out fromthe compound having the formula II in the method according to theinvention. First of all, it appears to be essential that thepolymerization step is carried out in alkaline conditions, at least onemolar equivalent of a base being used.

It is furthermore surprising that the polymer formed with structuralunits having the formula III has good properties. The inventors wereable to prepare said polymer with a small chain length of between 50 and1000 units. Contrarily, a chain length of 1800 to 7000 units wasachieved in the prior-art method cited above. The chain length wasdetermined in an analysis of GPC with polystyrene as the standard, whichis a usual method of analysis.

In addition, the polymer thus obtained is a substantially linearpolymer, i.e. no branching-off of the chain of the polymer and nocross-linking of different polymer chains occur during thepolymerization. The linearity of the polymer formed is important for theprocessing; polymers with strongly branched and cross-linked chains canbe provided as layers on substrates with difficulty only. The linearityis furthermore important for the structure of a layer of a polymer withstructural units having the formula I. An increasing linearity of apolymer chain with structural units having the formula I increases theprobability that a certain orderly arrangement will arise in the layerat least locally. Such an orderly arrangement would seem to befavorable, for example, for the electrical characteristics of thepolymer. Furthermore, the polymer prepared by the method according tothe invention shows fewer defects in the polymer chain than a polymerprepared by the prior-art method. The presence of defects is in fact nolonger detectable by means of NMR, which means that the defect rate isbelow 1%. The smaller number of defects implies that the polymerresulting after elimination of the S(O)_(p)R₁ groups has a chain whichis conjugated over a greater length: the chain has a greater conjugationlength. It is suspected that this microscopic property manifests itselfin a higher mobility and a higher electroluminescence.

In addition, the small number of defects offers the possibility ofinfluencing the conjugation length. This influence may be exerted, forexample, in that the S(O)_(p)R₁ groups in the polymer are oxidized afterpolymerization such that p is equal to 1 for a portion of the groups andp is equal 2 for another portion. Since the elimination of the SOR₁ andSO₂R₁ groups takes place at different temperatures, a polymer may beformed which still comprises SO₂R₁ groups and accordingly has a shorterconjugation length.

It is an advantage of the method according to the invention that thegroup R₁ may be chosen from a wider range of groups. This variability islimited to a lesser extent by synthetic problems than is the variabilityof groups in the prior-art method.

Precursor polymers with the formula VI which can be prepared by themethod preferably comprise as the—Ar group an aromatic group chosen fromamong 1,4-phenylene, 2,6-naphthalenediyl, 1,4-naphthalenediyl, 1,4anthracenediyl, 2,6-anthracenediyl, 9,10-anthracenediyl, 2,5-thienylene,2,5-furanediyl, 2,5-pyrrolediyl, 1,3,4-oxadiazole-2,5-diyl,1,3,4-thiadiazole-2,5-diyl, 2,5-benzo[c]-furanediyl,2,5-benzo[c]-pyrrolediyl, 2,5-benzo[c]thienylene,thieno[3,2-b]thiophene-2,5-diyl, pyrrolo[3,2-b]pyrrole-2,5-diyl,pyrene-2,7-diyl, 4,5,9,10-tetrahydropyrene-2,7-diyl, 4,4′-biphenylene,phenantrene-2,7-diyl, 9,10-dihydrophenantrene-2,7-diyl,dibenzofurane-2,7-diyl, dibenzothiophene-2,7-diyl, carbazole-2,7-diyl,of which the nitrogen-containing groups may be substituted on thenitrogen atom with a C₁-C₂₂-alkyl or a C₂-C₁₀-aryl group, while in allsaid groups R atoms on the aromatic rings may be substituted by a C₁-C₂₂linear or branched alkyl group, C₄-C,₁₄-aryl group, electron-donatinggroups such as C₁-C₂₂ linear or branched alkoxy and alkylthio groups,and halogen atoms or electron-absorbing groups such as cyano, nitro, andester groups, while the C₁-C₁₄-aryl group itself may be substituted byelectron-donating or electron-absorbing groups.

In general, metal bases, ammonium bases, and uncharged bases may be used,I as the base. Examples of uncharged bases include triethyl amine,pyridine and noninore phosphazene bases like1-tert-butyl-4,4,4-tris(dirnethylarino)-2,2-bis[tris(dimethylamino)-phosphoranylidenamino]-2 λ⁵, 4λ⁵-catenadi(phosphazene),1-tert-butyl-2,2,4,4,4-pentakis(dimethylaniino)-2,2-bis[tris(dimethylamino)-phosphoranylidenamino]-2λ⁵, 4 λ⁵-catenadi(phosphazene) andtert-butylimino-tris(dimcthylamino)phosphorane. Examples of metal andammonium bases are metal hydrides such as NaH, KH, metal hydroxides suchas NaOH, LiOH, KOH, metal alkoxides such as NaOMe, NaOEt, KOtBu, metalamides such as NaNH₂, NaN(SiMe₃)₂, lithium diisopropylamide,organometallic compounds such as n-butyllithium, Grignard reagentia, andsubstituted ammonium hydroxides.

Preferably, an aprotic solvent is used. There is a risk with proticsolvents that the base deprotonizes the solvent. It is found that thisweakening of the base adversely affects the polymerization. Instead of asingle solvent, a mixture of solvents may alternatively be used.Examples of classes of solvents are amides, amines, sulfons, sulfoxides,polyethers, cyclic ethers, and unsaturated ethers. Examples ofadvantageous solvents are inter alia Imonomethylformamide,dimethylformamide, imidazolidone, pyrrolidone, dimethylsulfoxide,dichloromethane, sulfolane, sulfolene, 1,3-diihethylimidazolidine-2-one,tetrahydrofurane, triethyleneglycol.

If the polymer comprising units having the formula I is desired in whicht is equal to 1 or 2, the polymer with units having the formula III isat least partly oxidized. It is found that an elimination of theS(O)_(t)R₁ group with t equal to 1 or 2 takes place at a lowertemperature than an elimination of the SR₁ group. It is important thatthe elimination temperature should be low, preferably lower than 300°C., especially in the manufacture of devices which comprise one orseveral layers of an organic material in addition to the layer of thepolymer having structural units of the formula I.

In an embodiment, the —Ar— unit chosen is the unit having the formula IV

in which formula

-   X is chosen from the group of O, S, NR_(6,)-   R₃ and R′₃ may be identical and are chosen from the group comprising    hydrogen, a chlorine, a bromine, a fluorine, and an iodine atom, a    C₁-C₄-alkyl, a carbonitryl, tnhalomethyl, hydroxy, nitro, amino,    carboxyl, sulfoxyl, sulfonate and carbonate group, and a substituted    and non-substituted phenyl, alkylaryl, and arylalkyl, alkoxy, and    thioalkoxy group, and-   R₆ is chosen from the group comprising a hydrogen atom and C₁-C₂₀    alkyl, aryl, C₁-C₂₀-alkylaryl, and arylalkyl group.

In this embodiment, the polymer with structural units having the formulaI is a precursor polymer of polythienylene-vinylene, whichpolythienylene-vinylene is also referred to as PTV. PTV hassemiconducting properties, which is why the material is used inter aliaas a p-type semiconductor layer in a transistor. An advantage of PTVover other semiconductors is its easy processability. A layer of thereadily soluble precursor polymer may be provided by a coatingtechnique, whereupon elimination to PTV is easy. The layer of PTV is notattacked if this layer is used as a substrate for a subsequent layer ofa different material.

In an alternative embodiment, the —Ar— unit chosen is the unit havingthe formula V

in which formula

-   R₅, R′₅, R″₅, and R″′₅ may be identical and are chosen from the    group comprising a hydrogen, chlorine, bromine, fluorine, and iodine    atom, and C₁-C₂₂-alkyl, carbonitryl, trihalomethyl, hydroxy, nitro,    amino, carboxyl, sulfoxyl, sulfonate, and carbonate group, and an    optionally substituted phenyl, C₁-C₂₂-alkylaryl and arylalkyl,    C₁-C₂₂-alkoxy, and C₁-C₂₂thioalkoxy group.

In this embodiment, the polymer with structural units having the formulaI is a precursor polymer of polyparaphenylene-vinylene, whichpotyparaphernylene-vinylene is also referred to as PPV. PPV is highlysuitable for use as an electroluminescent material for use in alight-emitting diode which consists at least partly of polymericmaterial. Advantageous examples of PPV and PPV precursors have as theirR₅ group a phenyl group or a 3,7-dimethyloctyl-1-oxy group. The unit ofa phenyl-substituted PPV is a 2,5-bis(1,1′-biphenyl). In contrast to the1,1 ′-bis(4,4′-biphenyl), the aromatic system of a unit of the polymericchain in the phenyl-substituted PPV is limited to a single phenylenegroup.

The second object is achieved in the method of preparing a compoundhaving the formula II, in that H—Ar—H reacts with R₁SH and R₂—(C═O)—Hand with R′₁SH and R′₂-(C═O)—H so as to form the compound having theformula II.

It was surprisingly found that the compound having the formula II can bedirectly prepared from H—Ar—H, a thiole R₁SH, and an aldehyde R₂—(C═O)—Hwithout a synthesis of the compound having the formula X beingnecessary. Preparation takes place in an acidic solution, which has theadvantage that no polymerization takes place in principle duringpreparation. Aldehydes R₂—(C═O)—H and R′₂—(C═O)—H which are used, forexample, are acetaldehyde, benzaldehyde, or p-formaldehyde. R₂ and R′₂may be different, but preferably they are the same. Preferably,thiophenol or alkylmercaptane is chosen for R₁SH and R′₁SH. R₁ and R′₁may be different, but preferably they are the same. Favorable examplesof H—Ar—H are thiophene and dialkoxybenzene. Examples of acids in theacidic solution are hydrochloric acid and hydrobromic acid.

It is an advantage of the method that substituents can be readilyintroduced into the polymer in a simple manner through variation of thegroups R₂ and R′₂. These substituents are present not only in thepolymer with structural units having the formula I, but also in thepolymer arising therefrom through elimination of the S(O)_(t)R₁ groupand having electroluminescent or semiconducting properties. Theproperties of said polymers can be adjusted by means of thesubstituents.

Furthermore, compounds having the formula II were prepared, in whichformula

-   Ar is an aromatic cyclic system with 4 to 20 carbon atoms, which may    be substituted with a substituent chosen from the group comprising a    non-branched C₁-C₂₀-alkyl, C₃-C₂₀-alkoxy, C₁-C₂₀-alkylsulfate, a    branched C₃-C₂₀-alkyl, phenyl or benzyl group, and which may    comprise up to 4 heteroatoms chosen from the group comprising    oxygen, sulfur, and nitrogen in the aromatic cyclic system,-   R₁ and R′₁ are chosen from the group comprising a non-branched    C₁-C₂₀-alkyl group, a branched C₃-C₂₀-alkyl group, a cyclic alkyl    group, a C₁-C₄-alkyl-substituted cyclic alkyl group, a C₄-C₁₄-aryl    group, and a benzyl group, which groups may comprise heteroatoms,-   R₂ is chosen from the group comprising a C₁-C₂₀-alkyl and    C₄-C₂₀-aryl group, which groups may comprise substituents, and-   R′₂ is chosen from the group comprising a hydrogen atom, a    C₁-C₂₀-alkyl, and a C₄-C₂₀-aryl group, which groups may contain    substituents.

In the compounds according to the invention, R₂ comprises an alkyl oraryl group. This group may be substituted with a substituent such assulfate, sulfonic acid, hydroxide, cyanide, nitro, amino, carboxyl, andcarbonyl. If R₂ and R₂′ are different and R₁ and R₁′ are different,stereo isomers and other isomers of the exemplary class of compoundshaving the formula II may be formed. The class of compounds having theformula II, however, should be interpreted such that it also includesthe stereo isomers and other isomers.

Furthermore, polymers comprising structural units having the formula IIIwere prepared. These polymers result from the method of formula Iwithout an additional oxidation being carried out. It was found that thepolymers comprising structural units having the formula II are stable inthe air for at least a number of weeks, in contrast to polymerscomprising structural units having the formula I with p equal to 1 or 2.The polymers comprising structural units having the formula III are thusfavorable intermediate products which can be stored and transportedwithout problems.

Furthermore, polymers comprising structural units having the formula Iwere prepared, which polymers have a chain length of at least 50 and atmost 1000 units, in which formula I Ar is an aromatic system with 4 to 6carbon atoms, which system may possibly be substituted and may contain aheteroatom. It is assumed that the mechanism for the formation ofprecursor polymers, for example comprising structural units having theformula I, proceeds via a true monomer formed in situ, probably ap-quinodimethane system. Polymerization of this true monomer seems to beself-initiated. The chain length of a formed polymer thus cannot beinfluenced by the reaction time or the quantity of initiator, but shouldbe regarded as a material characteristic. The fact that the chain lengthof the polymer according to the invention is smaller than the chainlength of the same polymer prepared by the prior-art method appears tobe caused by a different behavior of the SR₁′ group with respect to Y,which is chosen from Cl, Br, F, and tosylate. This explanation issupported by an embodiment of the prior-art in which Y and Y′ are equalto n-butylsulfinyl (n-C₄H₉SO). In this embodiment, the molar weight is3800 g/mole, which corresponds to a chain length of approximately 19.

Furthermore, a composition of polymers with structural units having theformula IX was prepared

in which:

-   Ar is an aromatic cyclic system with 4 to 20 carbon atoms, which may    be substituted with a substituent chosen from among a non-branched    C₁-C₂₀-alkyl, C₃-C₂₀-alkoxy, C₁-C₂₀-alkylsulfate, a branched    C₃-C₂₀-alkyl, phenyl or benzyl group and which may comprise up to 4    heteroatoms chosen from the group comprising oxygen, sulfur, and    nitrogen in the aromatic cyclic system,-   R₂ and R″₂ are chosen from the group comprising a hydrogen atom and    a C₁-C₂₀-alkyl and C₄-C₂₀-aryl group, which groups may optionally    comprise substituents, and-   Z is chosen from a group comprising S(O)_(p)R₁, OR₂, in which p is    equal to 0, 1 or 2, and R₁ and R₂ are chosen from the group    comprising a non-branched C₁-C₂₀-alkyl group, a branched    C₃-C₂₀-alkyl group, a cyclic C₄-C₂₀-alkyl group, a    C₁-C₄-alkyl-substituted cyclic C₄-C₂₀-alkyl group, a phenyl group,    and a benzyl group, which groups may contain heteroatoms,    wherein a first fraction of the composition comprises polymers with    structural units having the formula IX with Z equal to S(O)_(p)R₁    and a chain length of 50 to 1000 units, and a second fraction of the    composition comprises polymers with a chain length of more than 1000    units.

Solutions of precursor polymers prepared by different methods may bemixed in order to attune the viscosity to the envisaged application. Themixing possibility has the advantage that the viscosity of the solutioncan be adjusted as desired.

The third object of the invention is achieved in the method of preparinga conjugated polymer of the kind mentioned in the opening paragraphs inthat a polymer comprising structural units of formula III is converteddirectly into the polymer comprising structural units of formula VI byheating under catalysis of acid. This direct conversion is in fact anelimination of the sulfide group SR₁. The inventors are of the opinionthat the elimination of the SR₁-group occurs via a sulphonium-ion, assaid sulphonium ion has an lower elimination temperature than thesulfide SR₁-group.

The method of preparing a conjugated polymer has important advantagesabout the two-step elimination method comprising the oxidation of thesulfide group to a sulfinylgroup—SOR₁. It was observed that theoxidation is very sensitive for the amount of oxidizer. While using moreor less than one equivalent of oxidizer, a polymer withsulfonylgroups—SO₂R₁ or with sulfidegrpups—SR₁ next tosulfinylgroups—SOR₁ were obtained regularly. It further turned out thatthe—SO₂R₁ and the—SR₁—groups are less easily eliminated than the—SOR₁-group, and actually were not eliminated at all in many eliminationexperiments. The resulting polymers showed only a moderateelectroluminescent efficiency and a somewhat nasty injection barrier,when applied in an electroluminescent device. Now having found a betterelimination method, it appears that this moderate electroluminescentefficiency can be ascribed to the not eliminated—SOR₁—and—SR₁—group,which lead to an interruption of the conjugation in the conjugatedpolymer.

Experiments have shown, that the acid catalysed elimination ofthe—SR₁—group from the polymer comprising structural units of theformula III works in solution and after applying said precursor polymeras a layer onto a substrate. The amount of acid used can be as little as5 mole %, of the amount of the precursor polymer which includes a largenumber of sulfide groups. This shows that the acid is a true catalyst.

The fourth object of the invention is achieved in the method ofmanufacturing a layer of the kind mentioned in the opening paragraphs inthat the solution to be provided as a layer comprises a polymer withstructural units having the formula I, with a chain length of at least50 and at most 1000 units.

It was found that the solution of the precursor polymer with a chainlength of between 50 and 1000 has a viscosity of approximately 5 to 15mPa·s. This viscosity is approximately one order of magnitude smallerthan the viscosity of the known solution of the precursor polymer with achain length of more than 1000. This lower viscosity prevents theproblem that the solution of the precursor polymer stays behind indevices such as spin coating machines and filters. In addition, stepssuch as filtration and spin coating may be carried out at a higher speedand at normal pressures and temperatures. The precursor polymer with asmaller chain length may be prepared by the preparation method accordingto the invention.

In an embodiment, the solution to be provided as a layer also comprisesa polymer with structural units having the formula I and with a chainlength of at least 1000 units. Solutions of precursor polymers preparedby different methods may be mixed so as to attune the viscosity to theenvisaged application. The mixing possibility has the advantage that theviscosity of the solution can be adjusted as desired. The mixingpossibility may be advantageous not only for the processing properties,but also for the properties of the layer. The chain length is found toinfluence, for example, the luminescence of a polymer arising afterelimination of the S(O)_(p)R₁ group. The luminescence can accordingly beadjusted through mixing of solutions of precursor polymers of differentchain lengths.

In an alternative embodiment, the method starts with a solution of apolymer with structural units having the formula I, in which p is equalto 0, and the polymer with structural units having the formula I, inwhich p is equal to 0, is oxidized with a peroxide prior to theapplication of the solution as a layer, whereupon a polymer withstructural units having the formula I is created in which p is equal to1 in at least a proportion of the units. It was found that the precursorpolymer with p equal to 0 has a good stability. It is accordinglyfavorable in practice to start with the precursor polymer with p equalto 0 previously prepared. The oxidation into the precursor polymer withp equal to 1 is achieved with a peroxide, such as m-perbenzoic acid. Ifit is desired that the conjugated chain contains as few defects aspossible, one molar equivalent of peroxide should be added in theoxidation for each structural unit of the chain. Elimination of theSO₂R₁ groups is found to take place at a higher temperature than theelimination of the SOR₁ groups. If the layer is provided on a substrateof polymeric material, it is highly preferable for p to be equal to 1;degradation of the substrate may occur in the case of heating of thesubstrate and the layer up to the elimination temperature of the SO₂R₁group.

The fifth object of the invention is achieved in that the polymer isprepared from at least a polymer with structural units having theformula I, with a chain length of at least 50 and at most 1000 units,

in which formula I:

-   -   t is equal to 0, 1, or 2,    -   R₁ is chosen from the group comprising a non-branched        C₁-C₂₀-alkyl group, a branched C₃-C₂₀-alkyl group, a cyclic        C₄-C₂₀-alkyl group, a C₁-C₄-alkyl-substituted cyclic        C₄-C₂₀-alkyl group, a phenyl group, and a benzyl group, which        groups may comprise heteroatoms, and    -   R₂, R′₂ and Ar are identical to R₂, R′₂, and Ar, respectively,        in formula VI.

The electronic device according to the invention has a number ofadvantages thanks to the use of polymers with chain lengths between 50and 1000, in which the Ar group comprises an aromatic system of 4 to 6carbon atoms and possibly a heteroatom, and is possibly substituted. Thepolymers were found to have fewer defects. As a result, the polymer hasbetter properties. The use of the polymer with a shorter chain lengthfurthermore reduces the cost price of the device; not only is the methodof preparing the precursor polymer easier than the known method, but theprepared solution of the precursor polymer also has a lower viscosityand is thus easier and faster in processing.

In a first embodiment, the device according to the invention is alight-emitting diode in which —Ar— is equal to the unit having theformula V. Light-emitting diodes manufactured partly from polymericmaterial are important elements in the development of displays.

In a second embodiment, the device according to the invention is anintegrated circuit in which —Ar— is equal to the unit having the formulaIV. Integrated circuits which are at least partly manufactured frompolymeric material have the advantages of a low cost price and a highflexibility. They are highly suitable for use in transponders for theidentification of items. Such circuits may in principle also beintegrated with light-emitting diodes.

These and other aspects of the method of preparing a polymer withstructural units having the formula I, the method of preparing acompound having the formula VII, the method of manufacturing anelectronic device, and compounds having the formula II and polymerscomprising structural units having the formula III and I according tothe invention will now be described in more detail with reference todrawings and embodiments, in which:

FIG. 1 is a diagrammatic cross-sectional view of a transistor, and

FIG. 2 is a diagrammatic cross-sectional view of a light-emitting diode.

The transistor 1 depicted in FIG. 1 comprises an electrically insulatingsubstrate 2, a first layer 3 thereon of a polymeric material, forexample polyaniline, comprising electrically conductive portions andoffering space to a source electrode 31 and a drain electrode 32. Theelectrically non-conductive portions of the first layer 3 may beremoved. The organic semiconductor layer 4 comprisingpolythienylene-vinylene prepared by the method according to theinvention has a channel 41 whose channel length is referenced 411. Anelectrically insulating layer 5, for example made of polyvinylphenol,covers the layer 4 and insulates the gate electrode 61 from the channel41. The gate electrode forms part of a second conductive layer 6 whichis manufactured, for example, from doped polyaniline. The electricallynon-conductive portions of this second conductive layer may be removed.

Other examples of field effect transistors comprise bottom-gatestructures and transistors with alternative organic polymers ornon-polymeric layers for the insulating and conducting portions. Thetransistor may form part of a wider circuit, such as an inverter, anoscillator, or an integrated circuit. It is possible to manufacture notonly a field effect transistor, but also a bipolar transistor with asemiconductor layer of polythienylene-vinylene by the method accordingto the invention.

FIG. 2 diagrammatically shows a cross-section through a light-emittingdiode 101. This electronic device comprises a substrate 111, a firstelectrode layer 112, a first relief structure 113, an electroluminescentlayer 114, and a second electrode layer 115. The substrate 111 comprisesglass, the first electrode layer comprises ITO, and the second electrodelayer comprises Al. The first relief structure 113 compriseselectrically conductive poly(3,4-ethylenedioxy)-thiophene,(PEDOT), andthe electroluminescent layer 114 comprises polyphenylene-vinlyene. Thepatterns 121, 122 have a dimension of 100 μm in length and width. Therelief structure 113 and the electroluminescent layer 114 each have athickness of the order of 100 nm. The light-emitting diode ismanufactured through sputtering of ITO onto the substrate 111. Asolution of polyvinylphenol and the cross-linking agenthexamethoxymethylmelamine (HMMM) in propyleneglycolmethylether acetateis spin-coated onto the ITO, whereby a layer of 200 nm is formed. Thelayer is exposed in accordance with a chosen pattern and washed, suchthat a patterned layer 116 is formed. The polyvinylphenol is removed inthose regions where the patterns 121, 122 are to be formed. An aqueouscolloidal solution of PEDOT, poly(styrenesulfonic acid), and aphoto-initiator is provided on the substrate by means of spin coating,so that a layer is formed. The layer is exposed in accordance with adesired pattern and developed in water, so that the relief structure 113is created. Then the oxidized precursor polymer ofpolyparaphenylenevinylene is provided as the layer 114. This precursorpolymer comprises structural units having the formula I, in which Ar isequal to benzyl, and t is equal to 1. The sulfoxy group is eliminated byheating, and a layer of polyparaphenylenevinylene is formed. Finally,the second electrode layer is provided by means of sputtering.

EMBODIMENT 1

Preparation of 2,5-bis(phenylthiomethyl)thiophene, the Compound havingthe Formula II with Ar Equal to Thienylene—the Unit having the FormulaIV with X Equal to S, R₃, R′₃ Equal to H—, R₂ and R′₂ Equal to H, and R₁and R₁′ Equal to Phenyl.

A mixture of paraformaldehyde (45 g) and 30% hydrochloric acid (200 ml)is heated for 90 minutes at 60° C. The solution thus formed is cooleddown, whereupon a mixture of thiophenol (156 ml) and thiophene (57 ml)is added in 20 minutes at 30-35° C. The mixture is heated at 70-75° C.for three days under mechanical stirring and subsequently poured into amixture of toluene and water. After the layers have separated and theorganic layer has been washed with water, the organic layer is filteredthrough Celite and washed with ammonia. While stirring, the toluene isevaporated. The solid residue is filtered through 200 g silica gel, forwhich a mixture of hexane and some ethyl acetate is used as the eluent.The resulting effluent is evaporated, so that a residue remains. This isrecrystallized from a mixture of hexane and ethyl acetate. The filtrateis given an aftertreatment. The total yield is 108.0 g (46%, based onthiophene).

EMBODIMENT 2

Preparation of 2,5-bis(butylthiomethyl)thiophene, the Compound havingthe Formula II with Ar Equal to Thienylene, R₂ and R₂′ Equal to H, andR₁ and R₁′ Equal to Butyl.

250 ml 33% sodium hydroxide solution is slowly added to a mixture ofbutanethiole (157 ml), 2,5-bischloromethylthiophene (138 g), 250 mltoluene, and 2.0 g benzyltriethylammonium chloride. The temperature ofthe reaction mixture gradually rises to 60° C. during this, for whichsome cooling is necessary. The mixture is stirred for 4 hours at 60° C.,whereupon it is cooled down. The organic and the watery layer in themixture are separated, and the organic layer is washed with 2×250 mlwater. Then the organic layer is evaporated, so that a residue remains.This residue is purified by means of Kugelrohr distillation. The firstfraction obtained is 22 g monobutylthiomethylthiophene, the secondfraction is the desired product (134 g, 33% yield based onbutanethiole).

EMBODIMENT 3

Polymerization of 2,5-bis(phenylthiomethyl)thiophene into the Polymerwith Structural Units having the Formula I in which Ar is Equal toThienylene, R₂ and R₂″ are Equal to H, R₁ is Equal to Phenyl, and t isEqual to 0.

A solution of lithium diisopropylamine is prepared in that 30 ml 2.4 Nbutyllithium in hexane is added to diisopropylamine (8.0 g) in 75 ml THFat −30° C. This solution is stirred for 15 minutes. Then it is cooleddown to −70° C. At this temperature, a solution of2,5-bis(phenylthiomethyl)thiophene (22 g) in 225 ml THF is added. Thedark solution is heated to 0° C. over a period of three hours. After theaddition of 100 ml water, the watery and the organic layers areseparated, and the organic layer is washed with another 100 ml water.The solution is partly evaporated, and the residue (c. 100 ml) is slowlyadded to 200 ml methanol under thorough stirring. The supernatantsubstance is decanted from the viscous oil, which oil is washed with alittle methanol. Drying of the viscous oil in high vacuum yields thepolymer mentioned above in the form of a foam. ¹H-NMR (CDCl₃): δ3.2 (bm,2H), 4.4 (bt, 1H), 6.3 (bs, 2H), 7.0-7.3 (m, 5H). Small signals areobserved at 4.1 CH₂SPh end groups) and 6.5 (bs).

EMBODIMENT 4

Alternative Polymerisation of 2,5-bis(phenylthiomethyl)thiophene intothe Polymer with Structural Units having the Formula I in which Ar isEqual to Thienylene, R₂ and R₂″ are Equal to H, R₁ is Equal to Phenyl,and t is Equal to 0.

A solution of 2,5-bis(phenylthiomethyl)thiophene (6,57 g, 20 mmole) andtetramethylethylenediamine (2,91 g, 25 mmole) in dry TBF (40 g) wascooled to −40° C. A 1.6 M solution of n-butyllithium in hexane (15.6 mL,25 mmole) was added. The reaction mixture was warmed to −10° C. in 1.5hours and quenched by adding 50 mL of water, giving organic fractionsand an aqueous fraction. The aqueous fraction was extracted with 2×50 mLof CH₂Cl₂. The combined organic fractions were washed with water (100mL), aqeous 1 M HCl solution (2×101 mL), water (100 mL), dried overMgSO₄ and precipitated in methanol (500 g). This sequence was repeatedthree times to afford a yellow-brown polymer after drying in vacuo.

EMBODIMENT 5

Polymerization of 2,5-bis(butylthiomethyl)thiophene into the Polymerwith Structural Units having the Formula I in which Ar is Equal toThienylene—the Unit having the Formula IV with X Equal to S, R₃, R₃′Equal to H—, R₂ and R₂″ Equal to H, R₁ Equal to Butyl, and t Equal to 0.

A solution of lithium diisopropylamine is prepared in that 30 ml 2.4 Nbutyllithium in hexane is added to diisopropylamine (8.0 g) in 75 ml THFat −30° C. This solution is stirred for 15 minutes. It is then cooleddown to −70° C. At this temperature, a solution ofbis(butylthiomethyl)thiophene (17 g) in 100 ml THF is added over a fewminutes. The dark solution is heated to 0° C. over a period of 2 hours.Then the solution is put in ice and stirred for 3 hours at 0° C. 2 mlmethanol is added to the mixture, and then water is added. The productis extracted with toluene. Washing with water and evaporation yields thepolymer in the form of a viscous oil, said polymer comprising unitshaving the formula I in which Ar is thienylene, R₂ and R₂″ are equal toH, R₁ is equal to butyl, and t is equal to 0. ¹H-NMR (CDCl3): δ0.8 (m,3H), 1.2-1.6 (m, 4H), 2.3 (m, 2H), 3.2 (bm, 2H), 4.1 (bt, 1H), 6.4 (bs,1H), 6.5 (bs, 1H). Small signals are observed at 3.8 (bs, CH₂SBu endgroups) and 6.65 (bs).

EMBODIMENT 6

Oxidation of the Polymer with Structural Units having the Formula I inwhich Ar is Equal to Thienylene, R₂ and R₂″ are Equal to H, R₁ is Equalto Butyl, and t is Equal to 0 into a Polymer having Such StructuralUnits in which t is Equal to 1.

The polymer prepared from 2,5-bis(phenylthiomethyl)thiophene (9.0 g,27.4 mmole) is dissolved in 150 ml dichloromethane. While the solutionis cooled down to a temperature of between −15 and −20° C.,m-chloroperbenzoic acid (70-75%, 6.30 g, max. 27.4 mmole) is added inportions over a period of 10 minutes. A mixture is created thereby whichis stirred for one hour, during which the temperature is allowed to riseto 5° C. Then the mixture is poured into 500 ml methanol under thoroughstirring. This mixture is further processed. The result is 3.82 goxidized polymer.

EMBODIMENT 7

Polymerization of 2,5-bis(phenylthiomethyl)-1,1′-biphenyl, the Compoundhaving the Formula II in which Ar is Equal to 1,1′-biphenylene—the Unithaving the Formula V with R₅ Equal to Phenyl, R₅, R₅′, R₅″ Equal to H—,R₁ and R₁′ Equal to Phenyl, and R₂′ Equal to H.

A solution of lithium diisopropylamine is prepared from diisopropylamine(5.25 g, 52.0 mmole), n-hexyllithium in hexane (18.0 ml of a 2.4 Nsolution, 43.2 mmole), and 50 ml tetrahydrofurane in a conventionalmanner. A solution of 2,5-bisphenylthiomethyl-1,1′-biphenyl (15.83 g,39.8 mmole) in 100 ml tetrahydrofurane is added to this solution at atemperature lower than −60° C. over a period of 10 to 15 minutes. Thesolution is heated to −10° C. in 90 minutes and is then stirred at −5 to−10° C. for another 90 minutes. Water (100 ml) is added, which givesrise to a two-phase system of an aqueous layer and an organic layer. Thelayers are separated and the organic layer is washed with 100 ml water.Then the solvent is evaporated from the organic layer, so that thepolymer remains. The polymer comprises structural units having theformula I in which Ar is equal to 1,1′-biphenylene, R₁ is equal tophenyl, R₂ and R₂″ are equal to H, and t is equal to 0.

EMBODIMENT 8

Direct Elimination of —SR₁-group from a Precursor Polymer ofpolyphenylene-vinylene by Heating Under Catalysis of Acid

To a solution of 100 mg phenylsulfide precursor ofpoly-3-(4-(3,7-dimethyloctyloxy)phenyl)-1,4-phenylenevinylene in 10 mltoluene 0,005 grams of p-toluenesulfonic acid is added. The solution isrefluxed during 4 hours in a nitrogen atmosphere. In this 4-hour period,the solution turns red and fluorescent. GPC chromatography is done,after 1 hour, in order to test the precursor polymer and the resultingpolymer. The precursor shows a main peak at 220 nm with an intensity=0.5AU and a second peak at 303 nm with an intensity of 0.15 AU. Theresulting polymer shows a first peak at 230 nm at an intensity of 0.28AU, a second peak at 303 nm with an intensity of 0.14 AU and a thirdpeak at 446 nm with an intensity of 0.18 AU. This results show that aconjugated system has been formed by elimination of the phenyl sulfidegroup. The precursor polymer has a number average molecular weight M_(n)of 13,000 g/mole and a weight average molecular weight M_(w) of 24,000g/mole. The resulting polymer has a M_(n) of 16,000 g/mole and an M_(w)of 29,000 g/mole.

EMBODIMENT 9

Second Example of Direct Elimation of —SR₁-group

A degassed solution of 1 (0.91 g, 3 mmoles) and p-toluenesulfonic acid(28.5 mg, 0.15 mmoles) in toluene (75 mL) was heated under reflux fortwo hours. The resulting deep-blue solution was cooled to roomtemperature and concentrated in vacuo. The crude material was dissolvedin THF and precipitated in methanol. This procedure was repeated twotimes.

EMBODIMENT 10

Third Example of Direct Elimation of —SR₁-group

A degassed solution of 1 (0.76 g, 3 mmoles) and p-toluenesulfonic acid(28.5 mg, 0.15 mmoles) in toluene (75 mL) was heated under reflux fortwo hours. The resulting deep-blue solution was cooled to roomtemperature and washed with aqueous 0.5 M NaHCO₃ (2×30 mL) anddemineralised water (2×30 mL). The organic fraction was concentrated invacuo. The crude material was dissolved in THF and precipitated inmethanol. This procedure was repeated two times.

EMBODIMENT 11

Fourth Example of Direct Elimination of SR₁-group

The precursor polymer 4 was spincoated from a 0.5 weight % chloroformsolution onto a regular MISFET test substrate. The precursor polymer 4was converted into 5 by annealing the substrate at 180° C. in anitrogen/HCl atmosphere (partial HCl pressure: 10⁻³ bar) for 45 min.After the conversion, the substrate was allowed to cool to roomtemperature in a flow of pure nitrogen in order to remove traces ofacid.

1. A method of preparing a polymer which comprises structural units of formula I,

in which formula: Ar is an aromatic cyclic system with 4 to 20 carbon atoms, which may be substituted with a substituent chosen from the group consisting of a non-branched C₁-C₂₀-alkyl, a C₃-C₂₀-alkoxy, a C₁-C₂₀-alkylsulfate, a branched C₃-C₂₀-alkyl, a phenyl group and a benzyl group and which may comprise up to 4 heteroatoms chosen from the group consisting of oxygen, sulfur and nitrogen in the aromatic cyclic system, t is equal to 0, 1 or 2, R₁ is chosen from the group consisting of a non-branched C₁-C₂₀-alkyl group, a branched C₃-C₂₀ alkyl group, a cyclic C₄-C₂₀-alkyl group, a C₁-C₄-alkyl-substituted cyclic C₄-C₂₀-alkyl group, a phenyl group and a benzyl group, which groups may comprise heteroatoms, R₂ and R″₂ are each chosen for the group consisting of a hydrogen atom, a C₁-C₂₀-alkyl group, and a C₄-C₂₀-aryl group, which groups may comprise substituents, characterized in that the method starts with a compound having the formula II

in which formula R′₁ is chosen from the group consisting of a non-branched C₁-C₂₀-alkyl group, a branched C₃-C₂₀-alkyl group, a cyclic alkyl group, a C₁-C₄-alkyl-substituted cyclic alkyl group, a phenyl group, and a benzyl group, which groups may comprise heteroatoms, R₁, R₂ and Ar are equal to R₁, R₂ and Ar in formula I, and R′₂ is chosen from the group consisting of a hydrogen atom, a C₁-C₂₀-alkyl group, an a C₄-C₂₀-aryl group, which groups may comprise substituents, and that the polymer with structural units of the formula I is prepared through polymerization with the aid of a base into a polymer which comprises units having the formula III

in which formula R₁, R₂ and Ar are equal to R₁, R₂ and Ar in formula II, and R″2 is chosen from the group comprising R₂ and R′₂, and for the preparation of the polymer with units having the formula I, in which formula t is equal to 1 or 2, through oxidation of at least a number of the units of the polymer having the formula III.
 2. A method as claimed in claim 1, characterized in that the method starts with a compound having the formula II in which —Ar— is the unit having the formula IV

in which formula X is chosen from the group consisting of O, S, NR₆, R₂ and R′₃ are chosen from the group consisting of a hydrogen atom, a chlorine atom, a bromine atom, a fluorine atom, and an iodine atom, a C₁-C₄-alkyl group, a carbonitryl group, a trihalomethyl group, a hydroxy group, a nitro group, an amino group, a carboxyl group, a sulfoxyl group, a sulfonate group, a carbonate group, a substituted and non-substituted phenyl group, an alkylaryl group, an alkalkyl group, an alkoxy group, and a thioalkoxy group, and R₆ is chosen from the group consisting of a hydrogen atom, a C₁-C₂₀-alkyl group, an aryl group, a C₁-C₂₀-alkylaryl group and an arylalkyl group.
 3. A method as claimed in claim 1, characterized in that the method starts with a compound having the formula II in which —Ar— is the unit having the formula V

in which formula R₅, R′₅, R″₅ and R′″₅ are chosen from the group consisting of a hydrogen atom, a chlorine atom, a bromine atom, a fluorine atom, an iodine atom, a C₁-C₂₂-alkyl group, a carbonitryl group, a trihalomethyl group, a hydroxy group, a nitro group, an amino group, a carboxyl group, a sulfoxyl group, a sulfonate group, a carbonitrate group, an optionally substituted phenyl group, a C₁-C₂₂-alkylaryl group, a C₁-C₂₂-arylalkyl group, a C₁-C₂₂-alkoxy group, and a C₁-C₂₂-thioalkoxy group.
 4. A composition of polymers with structural units having the formula IX:

Ar is an aromatic cyclic system with 4 to 20 carbon atoms, which may be substituted with a substituent chosen from the group consisting of a non-branched C₁-C₂₀-alkyl, group, a C₃-C₂₀-alkoxy group, a C₁-C₂₀-alkylsulfate group, a branched C₃-C₂₀-alkyl group, a phenyl group and a benzyl group and which may comprise up to 4 heteroatoms chosen from the group consisting of oxygen, sulfur and nitrogen in the aromatic cyclic system, R₂ and R₂′ are chosen from the group consisting of a hydrogen atom and C₁-C₂₀-alkyl and a C₄-C₂₀-aryl group, which groups may comprise substituents, and Z is chosen from a group consisting of S(O)pR₁, OR₂, in which p is equal to 0, 1 or 2, and R₁ and R₂ are chosen from the group comprising a non-branched C₁-C₂₀-alkyl group, a branched C₃-C₂₀ alkyl group, a cyclic C₄-C₂₀ alkyl group, a C₁-C₄-alkyl-substituted cyclic C₄-C₂₀-alkyl group, a phenyl group, and a benzyl group, which groups may contain heteroatoms, wherein a first fraction of the composition comprises polymers with structural units having the formula IX with Z equal to S(O)pR₁ and a chain length of 50 to 1000 units, and a second fraction of the composition comprises polymers with a chain length of more than 1000 units. 